1. Field of the Invention
The invention relates in general to an oscillator and a control circuit, and more particularly to a crystal oscillator and a control circuit thereof.
2. Description of the Related Art
Oscillators have been widely used in various applications for providing a system with accurate and stable frequency standard, such as clock signals. In short, an oscillator is served as a frequency source, or as an electronic device which itself can convert direct current (DC) power into alternative current (AC) power without external excited signals. In the course of oscillating, the oscillator usually uses a feedback amplifier to generate an oscillation signal. Thus, the performance of an oscillator is based on whether there is an accurate, stable oscillation signal.
In general, the frequency of the oscillation signal is the primary concern for the oscillator. However, the swing of the oscillation signal also affects the performance of the oscillation. For example, an oscillator can be implemented by using feedback resistors and inverse inverters, the performance of which, however, is required to be improved. In such oscillators, the swing of the oscillation signal may become too large or too small to be properly controlled. Moreover, different oscillators have different circuits, so that the generated oscillation signals are different from each other.
In addition to the difficulty in controlling inverse amplifiers, how to adjust current consumed by the oscillator also is required to be taken into consideration. In light of power saving, the oscillator is tuned to be operated at low power. At this time, in an environment where noise level is high, the oscillator may have problem generating an oscillation signal. Therefore, it is a subject of the industrial endeavors to provide an oscillator which has high performance of generating an accurate, stable oscillation signal.